Seat arrangements providing adjustable lumbar support

ABSTRACT

An assembly for incorporation in a seat back to provide adjustable lumbar support comprises a platform element suspended by tension springs in a seat frame to support the cushioning of a back rest. The platform element has elongate lateral rails between which extend transverse wires that provide the platform support. A Bowden cable is linked between respective portions of each of the rails to apply a force of longitudinal compression, whereby the rails are caused to be hinged outwardly at an articulation point to vary the lumbar support provided by the transverse wires.

This invention concerns improvements in and relating to seatarrangements providing adjustable lumbar support, and more especially toa seat structure that is particularly adapted for use in an automobileseat of the kind wherein a platform element providing support for theupholstery of the seat is resiliently suspended in a seat frame.

It is known, see for example EP 0 169 293, that an assembly forincorporation in a seat back to provide adjustable lumbar support maycomprise a platform element adapted to be suspended in a seat frame tosupport the cushioning of a back rest, said platform element includingtwo elongate lateral rails between which extend transverse members thatprovide the platform support, adjustable means being linked betweenrespective portions of each of said elongate rails to apply thereto aforce of longitudinal compression, whereby said rails are caused to bearched outwardly in the lumbar region of the back rest together with thetransverse members carried thereby.

Such an arrangement provides an adjustable and comfortable lumbarsupport which is of relatively simple design. It has the disadvantage,however, that the outward arching of the lumbar region of the back restis required to be caused by flexing of the elongate lateral rails, whichare of spring wire construction and must be of relatively heavy gauge tosupport the bending forces applied thereto by tension springs supportingthe arrangement in the seat frame and which are required to carry loadplaced upon the platform element. Thus a relatively high force oflongitudinal compression is required to cause the arching of the lateralrails, particularly when the platform element is providing minimumlumbar support and is in a relatively flat condition. Correspondinglyheavy forces are thus placed upon the adjusting arrangement, which mustbe linked between the extreme ends of the lateral rails to give themaximum mechanical advantage in applying a bending force to the rails.The places a limitation upon the available types of adjusting mechanismthat can be used, as well as requiring a significant space for theadjusting arrangement within the back rest itself.

It also has the further disadvantage, however, that although the degreeof lumbar support can be readily adjusted in the horizontal direction,the vertical position at which lumbar support is provided is determinedby the initial geometrical shape of the platform element and the pointsat which the compression forces are applied to the lateral rails, sothat it is impossible for an occupant of the seat to adjust the lumbarsupport in a vertical direction to meet individual requirements.

Other known systems are available to provide for vertical adjustment oflumbar support, but these have the disadvantage that they are notadaptable to the particular arrangement initially referred to. Also,such known systems require that a support element scuff up and down onthe back of the cushioning of the back rest, so that some form ofadditional sliding interface is necessary to allow free movement of thevertically adjustable support means.

It is a general object of the invention to provide an improvement on anassembly of the kind initially referred to.

It is a preferred object of the invention to overcome, or at leastreduce one or more of the above mentioned disadvantages.

In accordance with one aspect of the invention, this object is achievedin that the said lateral rails are provided with a hinged articulationpoint in the region of lumbar support, whereby outward arching of therails is effected by bending of the platform element in the form of aridge.

Surprisingly, it has been found that despite the fact that the outwardarching of the platform element forms a ridge or apex of increasinglyacute angle, this does not, as might be expected, cause discomfort tothe occupant of the seat, provided that the contouring of the platformelement and the cushioning supported thereby are appropriately adaptedto their purpose.

Preferably the lateral rails are freely hinged together in such a mannerthat they present a minimum restoring force tending to resist arching,and the platform element is suspended in the back rest in such a mannerthat the suspension springs themselves provide the restoring forcetending to return the lateral rails towards a rectilinear condition.

As arrangement in accordance with this aspect of the invention theinvention has the advantage that an adjustment mechanism is required toexert little force upon the platform element and may be linked betweenpoints on the lateral rails that are relatively closely spaced, i.e. notat the two extreme ends of the rail. This enables an adjusting mechanismsuch as a Bowden cable linkage to be used, such a linkage offering theadvantages of economy, simplicity and versatility.

Another aspect of the invention provides an assembly for incorporationin a seat back to provide adjustable lumbar support, comprising aplatform element adapted to be suspended in a seat frame to support thecushioning of a back rest, said platform element including two elongatelateral rails between which extend transverse members that provide theplatform support, wherein said platform element includes a transverselumbar region that is articulated together with said rails in the mannerof a trapezium linkage in order to enable variation of the angularattitude of said lumbar region relatively to the base of the trapezium,and said lumbar region is linked to adjusting means for varying theangle thereof relatively to an adjacent section of the platform element,the arrangement being such that said variation of said angle causes avertical displacement of the effective position of lumbar support.

In accordance with one embodiment of the invention, the said lumbarregion of the supporting platform may be formed by a separate rocketpanel that is pivotally linked between the rails of upper and lowerplatform sections, the rocker panel having an appropriately contouredsurface in the vertical section, whereby the vertical position of theeffective lumbar support provided thereby is varied with the angularattitude of the rocker panel.

Further preferred features and advantages of the invention will becomeapparent from the following description taken in conjunction with thedrawings, in which:

FIG. 1 is a front view of an assembly in accordance with the invention,shown suspended in the frame of a back rest of a vehicle seat;

FIG. 2 is a side elevation of the assembly illustrated in FIG. 1 withthe relative position of the supporting frame illustrated in brokenlines for reference;

FIG. 3 is a geometric diagram illustrating the effective ranges andpositions of adjustment of the assembly as illustrated in FIGS. 1 and 2,

FIG. 4 is a side elevation illustrating an alternative arrangement forproviding adjustment of the assembly of FIGS. 1 and 2.

FIG. 5 is a front elevation of the back rest of a seat incorporating anassembly according to the invention for providing adjustable lumbarsupport, and

FIG. 6 is a diagrammatic side elevation illustrating the geometricalarrangement of the platform element of the assembly of FIG. 1.

Referring to FIG. 1 and 2 of the drawings, there is illustrated theframe 1 of a seat back for the seat of an automobile. Suspended withinthe frame by means of tension springs 2 is an assembly, indicatedgenerally at 3, that serves as a platform element for supporting thecushioning and upholstery of the vehicle seat back. The platform element3 comprises an upper section 4 consisting of two generally verticallateral rails 5 formed by paper-wrapped steel cords between which aretensioned transverse wires 6 penetrating an intermediate vertical cord7. Such a construction is well known in the art, and a lower section 8of the pad is formed in similar manner from paper wrapped cords 9 andtransverse wires 10.

Secured to the upper section 4 by means of clips 11 embracing the rails5 is a sub frame 12 of formed wire, inturned ends 12A of which formpivots for a rocker panel 13. In the illustrated embodiment this isformed as a flanged sheet metal pressing although it could be formed bymoulding from synthetic plastics material. Synthetic plastics bushes 14secured within flanges 15 of the rocker panel 13 serve as journals forengagement by the ends 12A of the sub frame.

In a similar manner, the lower section 8 is provided with a sub frame 16in turned ends 16A of which engage in bushes 17 supported in the flange15.

The two sub frames 12 and 16 are spring biased relatively to the rockerpanel 13 by means of double acting torsion springs 18, each of whichextends around both of the adjacent inturned ends 12A and 16A of therespective sub frames, the springs 18 serving to bias the assembly sothat the sections 4 and 8 and the rocker panel 13 are urged towards therelative angular positions illustrated in FIG. 2.

The sub frame 12 is formed to include U-shaped loops 12B within whichare anchored double-socket ferrules 19 for the connection of two pairsof Bowden cables 20 and 21 respectively. Each pair of cables isassociated with a common actuating means 22, 23 respectively, which willbe described in more detail below.

An actuating cable 20A (FIG. 2) of each Bowden cable 20 is anchored to acorresponding flange 15A of the rocker panel 13, at 22. Likewise, anactuating cable 21A (FIG. 2) of each Bowden cable 21 is connected to ananchorage 24 supported in a U-shaped loop 16B of the sub frame 16.

Since the springs 18 cause the rocker panel 13 to be biased about thepivots 16A in a clockwise direction as viewed in FIG. 2 and to be biasedabout the pivots 12A in a clockwise direction as viewed in FIG. 2, thearrangement is such that when, starting from the position shown in FIG.2, the Bowden cable 20 is contracted to reduce the distance between theferrules 19 and the anchorages 22, the rocker panel 13 is pivoted in theanti-clockwise direction to vary its attitude relatively to the verticalplane, whereas when the Bowden cables 21 are contracted to reduce thedistance between the anchorages 24 and the ferrules 19, the trapeziumlinkage formed by the sub frames 12 and 16 and the rocker panel 13 iscaused to arch outwardly to the left as viewed in FIG. 2. Upon releaseof the respective Bowden cables, the springs 18 will tend to return theassembly to the position of FIG. 2.

Thus, by means of the controls 22 and 23 the platform element 3 can beadjusted to provide a variety of configurations of lumbar support, ascan be seen more clearly by reference to the diagram of FIG. 3.

In FIG. 3 the linkage points are given the same reference numerals as inFIG. 2, and thus the figure defined by the points 19,24,16A, and 12Ashows the attitude of the arrangement as in FIG. 2, in which the lumbarsupport is effectively provided at the point 16A. By control of theactuating means 20 the rocker panel 13 can be tilted progressively toprovide a range of adjustment in which the points 12A and 16A are movedthrough the positions 12A',16A' to positions 12A",16A" at which thelumbar support is provided at the point 12A". The contour of the panel13 is such that this has the effect of moving the lumbar supportprogressively through the vertical distance between the points 16A and12A".

Starting from the position in FIG. 2, control of the actuating means 21can move the point 24 vertically relatively to the point 19, to theposition 24', giving a range of horizontal adjustment of the lumbarsupport between the points 16A and 16A"'. Control of the actuating means20 can then be used, as already described, to move the lumbar supportvertically from the point 16A"' to the point 12A"'.

FIG. 4 illustrates an arrangement for actuating the Bowden cablelinkages 20 and 21 as described above. The outer sheath of each of thecables 20 is received in a ferrule block 25, whereas the internal cables20A are connected to a further block 26. The blocks 25 and 26 are inscrew threaded engagement with a lead screw 27 having left and righthanded screw sections 27A and 27B respectively. Thus rotation of thelead screw 27 is effective to cause the blocks 25 and 26 to be movedtowards or away from one another in order to actuate the Bowden cables20 in the sense required.

The Bowden cables 21 are connected in a similar manner to blocks 28 and29 located upon a similar lead screw 30.

The lead screws 27 and 30 can be actuated by means of a two-part controlknob 31, an inner portion 32 of which is fixed directly to the leadscrew 30 and is provided with appropriate finger recesses, not shown, tofacilitate rotation, and an outer circumferential portion 33 of which iscoupled to a spur gear 34 that is freely rotatable about an unthreadedsection of the lead screw 30.

The spur gear 34 is coupled via an idler gear 35 mounted on a rotaryshaft 36, to a further spur gear 37 that is fixed to the lead screw 27.

Thus the arrangement is such that by manipulation of the section 32 ofthe control knob, an occupant of the seat can vary the degree of lumbarsupport in the horizontal direction by means of the Bowden cables 21,whereas by independent rotation of the outer circumference 33 of thecontrol knob the Bowden cables 20 can be actuated to provide verticaladjustment of the point of lumbar support.

It will be appreciated that various alterations and modifications may bemade to the arrangement described above without departing from the scopeof the invention. Thus, in place of the two-part control knob 31,separate control knobs may be independently connected to the lead screws27 and 30 as illustrated in FIG. 1.

If desired, the trapezium linkage illustrated in FIGS. 1 and 2 may beprovided with stop means for preventing the linkage from snapping overcentre under load applied to the seat. Thus, for example, the rockerpanel 13 may be provided with an extended lug for engagement against thesub-frame 12 in order to limit the range of movement of the rocker panel13 relatively thereto, so that the pivot points 12A cannot pass overcentre between the points 16A and the points 19.

Referring to FIGS. 5 and 6 of the drawings there is shown anotherembodiment of the invention wherein like parts are indicated with thesame reference numerals as in FIGS. 1-4 and thus will not be describedagain in detail. In this arrangement the rocker panel 13 is omitted andadditional transverse wires 110 and 120 of heavier gauge than the wires10 are connected between the wires 9 by means of clips 130 and 140 tocomplete a rectangular outer frame of the lower section 8.

Clips 150 secure the transverse wire 110 to inturned ends of the cords5, whereby the clips 15 serve as hinges that allow the two sections 4and 8 of the platform element to be hinged relatively to one anotherabout the transverse wire 110.

The transverse wire 120 has hooked ends 120A that serve as anchoragesfor the grooved blocks 24 that fit within the hooks 120A and areanchored to the ends of Bowden cables 21A.

In a similar manner to the arrangement of FIGS. 1-4, a furthertransverse steel wire 12' is connected between the cords 5 by means ofclips 11' and has looped portions 12B' that serve to retain the groovedblocks 19 forming ferrules for the outer sleeves 21 of the Bowdencables.

Referring to FIG. 2, it will be seen that the lower section 8 of theplatform element and the lower sections of cords 5 extending between theferrules 19 and the clips 150 form a triangular ridge, the base of thetriangle being defined by the portions of Bowden cable 21A extendingbetween the anchorages 24 and ferrules 19. The Bowden cables 21A areheld under slight tension by means of the tensions springs 2 that anchorthe platform element 3 in the seat frame 1, and thus the angle of theapex of the triangular ridge is determined by the length of the Bowdencables 21A extending between points 24 and 19, which distance can beadjusted by manual actuation of the mechanism 23.

It will thus be seen that effective adjustment of the degree ofhorizontal lumbar support provided by the platform element 3 can beachieved in a simple manner by the mechanism 23 without the need for themechanism to exert significant force upon the platform element 3, andwithout the need for the adjusting mechanism to extend to the fullheight of the platform element 3. Thus a relatively compact simple andeconomical adjusting mechanism can be used.

We claim:
 1. An assembly for incorporation in a seat back to provideadjustable lumbar support comprising a platform element adapted to besuspended in a seat frame to support the cushioning of a back rest, saidplatform element including two elongate lateral rails between whichextend transverse members that provide the platform support, andadjustable means extending between upper and lower portions of each ofsaid elongate rails to apply thereto a force of longitudinalcompression, whereby said rails are caused to be arched outwardly in thelumbar region of the back rest together with the transverse membercarried thereby, and wherein said platform element includes a transverselumber region that is articulated between said upper and lower portionsof said rails about spaced, parallel transverse axes, in order to enablevariation of the angular attitude of said lumbar region in a verticalplane, and said lumbar region is connected to a second adjusting meansfor varying the angle on the platform element of said lumbar regionrelatively of upper and lower region of the platform element, thearrangement being such that said variation of said angle causes avertical displacement of the effective position of lumbar support.
 2. Anassembly according to claim 1 wherein said lumbar region of the platformelement is formed by a separate rocker panel that is pivotally linkedbetween the rails of upper and lower platform resections (4,8), therocker panel having a surface that is outwardly convex in the verticalsection, whereby the vertical position of the effective lumbar supportprovided thereby is varied with the angular attitude of the rockerpanel.
 3. An assembly according to claim 1, wherein said platformelement comprises a transversely flexible pad member supported in theback rest portion of a seat frame by means of tension springs linkedbetween an outer periphery of the said frame (1) and the said rails ofthe platform element.
 4. An assembly according to claim 3, wherein saidadjustable means comprises Bowden cable means linked between articulatedportions of said rails and coupled to first actuating means mounted inthe seat frame.
 5. An assembly according to claim 4, characterized inthat relatively articulated portions (4,8) of the said pad member (3)are respectively of major and minor dimension, and that the Bowden cablemeans (21,21A) are inked between a transverse axis adjacent that end ofthe minor portion (8) which is remote from the point of articulation(16A,150) and a transverse axis that is intermediate the ends of themajor portion (4), the said rails (5) being angled outwardly from saidintermediate transverse axis towards the said point of articulation topromote hinging of the pad member thereat.
 6. An assembly according toclaim 5, wherein each of said first and second actuating means comprisesa screw threaded shaft having oppositely screw threaded sections uponwhich are respectively located correspondingly threaded blocks anchoredto outer and inner elements of the Bowden cable means.
 7. An assemblyaccording to claim 6, wherein each said screw threaded shaft is coupledto a manual knob.
 8. An assembly according to claim 4 wherein Bowdencable means are linked between said lumbar region and an adjacent,relatively articulated portion of said platform element and coupled tosecond actuating means mounted in the seat frame.